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On the importance of backbone loop and peptide flip in the Walker sequence in F<sub>1</sub>-ATPase action

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Title On the importance of backbone loop and peptide flip in the Walker sequence in F1-ATPase action
 
Creator Ramasarma, T
 
Description 5-15
    The Walker sequence, GXXXXGKT,
present in all the six subunits of F1-ATPase exists in a folded
form, known as phosphate-binding loop (P-loop). Analysis
of the Ramachandran angles showed only small RMS
deviation between the nucleotide-bound and nucleotide-free forms. This
indicated a good overlap of the backbone loops.


The catalytic β-subunits
(chains
D,
E and F) showed significant changes in the Ramachandran angles and
the
side
chain torsion angles, but not the structural α-subunits (chains A, B and C). Most striking
among these are the changes associated with Va1160 and Gly161 corresponding to a flip in
the peptide unit between them when a nucleotide is bound (chains D or F compared to
nucleotide-free chain E).


    The conformational
analysis further revealed a hitherto unnoticed hydrogen bond between amide-N of
the
flipped Gly 161 and terminal phosphate-O of the nucleotide. This assigns a role for
this conserved amino acid, otherwise ignored, of making an unusual direct interaction
between the peptide backbone of the enzyme protein and the
incoming nucleotide substrate. Significance of this interaction is enhanced, as it is limited only to the catalytic
subunits, and also likely to involve a mechanical rotation
of bonds of the peptide unit. Hopefully this is part of the overall events
that link the chemical hydrolysis of ATP with the mechanical rotation
of this molecule, now famous as tiny molecular motor.
 
Date 2013-07-15T05:42:03Z
2013-07-15T05:42:03Z
2002-02
 
Type Article
 
Identifier 0975-0959 (Online); 0301-1208 (Print)
http://hdl.handle.net/123456789/19742
 
Language en_US
 
Rights CC Attribution-Noncommercial-No Derivative Works 2.5 India
 
Publisher NISCAIR-CSIR, India
 
Source IJBB Vol.39(1) [February 2002]